Thousands are expected to flock to West Hollywood Sunday for the L.A. Pride parade, an annual celebration of the gay, lesbian, bisexual and transgender community in Southern California.

The event, a colorful combination of revelry and political action, will begin at 11 a.m. and run until about 3 p.m., said Mike Stommel, spokesman for Christopher Street West, a nonprofit group organizing the event.

As in past years, celebrities and community leaders will be on hand for the festivities, but this year's grand marshals were chosen for their activism, Stommel said. They include the Rev. Troy Perry, founder of the Metropolitan Community Church in Los Angeles and one of the organizers of the first Pride parade in Hollywood in 1970; 13-year-old transgender activist Zoey and the cast and crew of "Transparent," the TV series produced by Amazon Studios that stars actor Jeffrey Tambor as a transgender woman.

Paradegoers will observe a moment of silence at noon. This year, Stommel said, marriage rights, currently under consideration by the U.S. Supreme Court, were of particular concern for the community.

Issues facing transgender people -- including violence and access to medical care -- are also in the spotlight.

"Obviously with Caitlyn Jenner, it's on not just the community's tongue," Stommel said. "It's really part of a big story that everyone is talking about around the world."

The L.A. Pride parade route will start at Crescent Heights Boulevard, heading west on Santa Monica Boulevard for about a mile and a half to Robertson Boulevard. Streets in the area will be closed between 5 a.m. and 5 p.m.; organizers, who expect more than 400,000 people to visit West Hollywood over the course of the weekend's events, warn that parking in the area will be challenging. (Further information about closures and parking options are available at the L.A. Pride website and from the City of West Hollywood.)